1. Field of the Invention
The present invention relates generally to a method and apparatus for controlling wireless power transmission, and more particularly, to a method and apparatus for controlling wireless power transmission through a wireless communication channel.
2. Description of the Related Art
Wireless power transmission refers to a technology that transfers electric energy through an electromagnetic wave, electromagnetic induction, or electromagnetic resonance, and therefore, provides power without a physical power line. Wireless power transmission will likely be a key technology for charging electronic devices, supplying power to and/or charging of electric vehicles, supplying power to remote areas, supplying power to ubiquitous wireless sensors, etc. Therefore, it is possible that wireless power transmission draw attention as a substitute for conventional scheme power supply using a physical power line.
For example, when wireless power transmission is used in a wireless charging system, the wireless charging system includes a wireless power supplying apparatus that supplies power and a wireless power receiving apparatus that receives power and charges a battery with the received power. The wireless power supplying apparatus measures a change in a load or a change in a resonant frequency in a wireless power transmission idle state, thereby detecting whether an object has been placed on a source resonance unit. When the object is detected, the power supplying apparatus transmits power to the object, and determines whether the object corresponds to an object requiring wireless charging, through an authentication procedure, such as exchanging an IDentifier (ID).
When authentication is successfully completed and the wireless power supplying apparatus determines that the object placed on the source resonance unit is an apparatus that may be wirelessly charged and then negotiates power transmission with the wireless power receiving apparatus.
When the negotiation is completed, the wireless power supplying apparatus starts wireless power supplying for charging the wireless power receiving apparatus, determines whether the wireless power receiving apparatus is fully charged, and stops transmitting power to the wireless power receiving apparatus when the wireless power receiving apparatus is fully charged.
In the wireless charging system as described above, the wireless power supplying apparatus performs wireless power transmission controlling through communication with the wireless power receiving apparatus. For example, a communication scheme between the wireless power supplying apparatus and the wireless power receiving apparatus may be an in-band communication scheme or an out-of-band communication scheme. The in-band communication scheme uses the same frequency band for a power supplying frequency band and a communication frequency band between the wireless power supplying apparatus and the wireless power receiving apparatus when wireless power transmission controlling is performed. The out-of-band communication scheme uses different frequency bands for the power supplying frequency and the communication frequency band between the wireless power supplying apparatus and the wireless power receiving apparatus when wireless power transmission controlling is performed.
In the in-band communication scheme, where the power supplying frequency band and the communication frequency band are the same, limitations on the strength of the power supplying frequency band and that of the communication frequency band may be different from each other.
For example, the Federal Communication Commission (FCC) standard limits a signal strength of a power supplying frequency band to 42 dBmA/m or less, and requires a signal strength of the communication frequency band to be 15 dBmA/m when a frequency band of 6.78 MHz is used for the power supplying frequency band and the communication frequency band. Accordingly, when the signal strength of the power supplying frequency band is greater than or equal to a predetermined level in the in-band communication scheme, the in-band communication scheme may fail to satisfy the FCC standard, and thus, may become inappropriate for communication for wireless power transmission controlling. Also, the in-band communication scheme may have a technical difficulty in performing bidirectional communication. Therefore, the out-of-band communication scheme may be utilized, which is not affected by the limitation on a power supplying signal strength and a communication signal strength because the power supplying frequency band and the communication frequency band are different from each other, and that relatively freely performs bidirectional communication.
FIG. 1 illustrates a conventional wireless power transmission controlling apparatus for a conventional out-of-band communication scheme.
Referring to FIG. 1, the wireless power transmission controlling apparatus includes a power unit 12, a power amplifier 14, a controller 16, a low pass filter 18, a resonance unit 20, an oscillator 22, a communication unit 24, and an antenna (ANT). The wireless power transmission controlling apparatus uses different frequencies for a resonant frequency output from the resonance unit 20, and for a communication frequency used by the communication unit 24. The oscillator 22 generates a frequency for communication. The wireless power transmission controlling apparatus performs various communication for providing wireless power through the frequency generated by the oscillator 22.
Accordingly, the conventional wireless power transmission controlling apparatus creates some problems for manufacturing and size efficiency in that it requires a separate circuit for generating a communication frequency that is different from a power supplying frequency, e.g., the oscillator 22, when the apparatus uses the out-of-band communication scheme.